Universal scaffolding machine



Oct. 15, 1957 w. B. SHEARD 2,809,804

UNIVERSAL SCAFFOLDING MACHINE Original Filed June 18, 1954 '7 Sheets-Sheet l lllm INVENTOR Oct. 15, 1957 w. B. SHEARD UNIVERSAL SCAFFOLDING MACHINE '7 Sheets-Sheet 2 Original Filed June 18, 1954 W. B. SHEARD UNIVERSAL SCAFFOLDING MACHINE v Original Filed June 18, 1954 Oct. 15, 1957 7 Sheets-Sheet 3' 6/; ATTORNEY Oct. 15, 1957 w. B. SHEARD 2,80

UNIVERSAL SCAFFOLDING MACHINE Original Filed June 18, 1954 '7 Sheets-Sheet 4 INVENTOR I filmmflyllmrd BY W Oct. 15, 1957 w. B. SHEARD 2,809,804

UNIVERSAL SCAFFOLDING MACHINE Original Filed June 18, 1954 7 Sheets-Sheet 5 INVENTOR fr /1/'; ATi'oRNEY Oct. 15, 1957 w. B. SHEARD 2,809,804

UNIVERSAL SCAFFOLDING MACHINE Original Filed June 18, 1954 7 Sheets-Sheet 6 @Jy. X 21 6' -7 /?/'J ATTORNEY Oct. 15, 1957 w. B. SHEARD 2,809,304

' UNIVERSAL SCAFFOLDING MACHINE Original Filed June 18, 1954. 7 Sheets-Sheet '7 INVENTOR Will/[177i fiy/ f/Zeard BY @wg d /J ATTORNEY United States. Patent UNIVERSAL SCAFFOLDING MACHINE William Byl Sheard, Pleasantville, N, Y., assignor to The Patent Scaffolding Co., Inc., Long Island City, N. Y., a corporation of New York 3 Claims. (Cl. 254-468) This invention relates to safety scaffolds, and more particularly to a scaffold winch for handling scaffolds such as used by painters, glaziers, pointers, window washers and maintenance crews working on the exterior of the faces of buildings orother elevated structures at some height above the ground.

The present application is a division of my copending application Serial No; 437,733, filed on June 18, 1954, now Patent No. 2,776,815. The universal safety winch of this invention may be either power driven or manually operated, depending upon the circumstances and availability of sources of power, such as electric current, compressed air or combustion motors.

It is often desired to elevate scaffolds with a considerable velocity and hand-operated winches have been found to be limited in this respect. However, it is again desirable to have a machine which may be hand-driven in the event of failure of the power source. My winch, when power driven, raises or lowers the scaffold structure attached thereto by means of a cable at considerable speeds and when idle, the braking mechanism therein prevents downward movement of the structure until the power unit is again operated in either direction. Thus,

the winch is particularly adapted for use by window washers on tall buildings, since one operator may control the raising or lowering of the structure by actuating the power units starter with one hand.

My winch provides a multiplicity of safety means to prevent accidental unreeling of the cable from the drum when such unreeling is not desired or dangerous to the crew supported by the scaffold structure. The winch combines a friction brake sysetm with a spring clutch in the same scaffolding machine, the latter being connected with a ratchet to form a one-way brake, either brake being adapted to hold the load by itself. Their mode of operation and their arrangement in the winch structure are such that one brake will offset the relatively weaker points of the other.

This novel multiple automatic brake construction in my winch immediately stops. any movement of the cable drum when the motor or handle is not operated. Theoperator is not required to control the action of the braking system since it will act automatically when necessary, i. e. at all times except when the driving shaft of the winch is actually rotated by hand or from the power source. The force exerted by the weight of the load attached to the free end of winch cable automatically operates the-braking system and locks the device until intentional rotational movement is imparted to the driving shaft of the winch. The cable drum is also easily disengageable from the driving mechanism in a very simple manner to permit unreeling of the cable independently of the power source.

Since the operation of the friction brake is affected rela e y l e by Wear, r at lea t ss t an ha of h S r l h. it is p e c o er t the e and is required to do most of the braking work. On the other hand, the spring clutch operates independently of the rest of the system and does not depend on the friction in the driving mechanism to operate automatically, as the friction brake. Therefore, it acts to hold the driving mechanism stationary and forces the friction brake to operate.

The invention further provides a simple, safe and obvious method of disengaging the driving mechanism when not under load, but being very difiicult to disengage when the winch is under load.

The disengaging mechanism also prevents overloading of the winch when the machine is unreeling cable and prevents the winding or spooling in the wrong, direction which could jeopardize the operation of the automatic load brakes.

Other features and attributes of my invention will become apparent in the course of the following description of two at this time preferred embodiments which are illustrated in the accompanying drawing, and the invention will be finally pointed out in the appended claims.

In the drawing,

Fig. 1 is a perspective view of the assembled universal scaffolding machine constructed in accordance with one preferred embodiment of my invention;

Fig. 2 is a vertical section taken along line 22 in Fig.1;

Fig. 3 is a section taken along line 33 in Fig. 2;

Fig. 4 is a section taken along line 4-4 in Fig 2;

Fig. 5 is a partial end view of the spring clutch, taken along line 55' in Fig. 3;

Fig. 6 shows another embodiment of the invention and is ise t o alerts lin 6 in Fig. 7;

Fig. 7 is a view, partly in section, taken along line 7-7 in Fig, 6; and

Fig. 8 is a section through the spring clutch, taken along line 8-8 in Fig. 7.

Similar characters of reference refer to identical ele-.l ments throughout the various views in the drawing.

Referring now in more detail to the drawing, and first to. Fig. 1, there is shown a support A, consisting of two suitably shaped stirrups 10 and 11, to which the shells 12. and 13 of winch casing B are secured by bolts 14, 14a, Stirrup 10 carries a guard rail support 15.

The winch is driven by an electric motor 17, operable through: witc x 18 y lever 19-, H we er, aerank' 56 may 'be attached to shaft 38 to adapt the winch to, manual operation.

The winch mechanism, and more particularly that em-. bodiment thereof wherein the winch may be either powerdriven or manually operated, is shown in Figs, 2,- to 4.. Referring first to Fig. 3 which is a longitudinal section through shells 12, 1 3 of casing B, there are shown bracing shafts 20a, 1), c, d, connecting shells 1 2, 13, inspaced relationship. A sheave wheel 21is mounted on shaft 20 for free rotational'movement between the two forks or extensions of a member 22 which' is mounted on shaft 23. Cable 24 is secured at its outer free end to cornice. hooks, outrigger beams or other appropriate anchorage (not shown) in the usual manner. As the cable 2, 4 enters the winch, it passes over sheave wheel 21 and down to, cable drum 25 to which its other. end is securelyattached. When the cable drum 2-5, on its shaft 26, is rotated in clockwise direction, as shown byarrow a in Fi'g; 2, the cable will spool on the drum barrel 25a, and when rotated in the counterclockwise direction, the cable will secured therein by a cotter pin 16 or the like. Oneend of; guide pin 2-7'follows the helical'grooves' 23a of shaft 23 and since these grooves are continuous and reverse themselves near the ends of shaft 23, member 22 with sheave wheel 21 travels back and forth between shells 12, 13, thereby evenly distributing the cable convolutions on the drum barrel 250. A sprocket 28 is keyed to shaft 23 and is driven by a roller chain 29, the chain in turn being driven by sprocket 30 keyed to shaft. 26. Sprocket 30 thus always rotates in unison with cable drum 25. The drive from shaft 26 to shaft 23 is so proportioned that the sheave wheel 21 traverses back and forth at a rate required to spool cable 24 evenly across barrel 25a of drum 25. Bearings 31, 31a (Figs. 3 and 4) at both ends of shaft 26 reduce the friction of the shaft 26 during the rotation thereof. Barrel 25a is limited at both its ends by flanges 32, 32a which prevent cable 24 from slipping off the barrel on either side thereof.

A partition wall 99 encloses with shell 12 the rotation transmitting mechanism and the friction brake. The winch is driven by an electric or air motor 17 energized by switch 19 or air valves respectively (Fig. 2). Motor 17 drives a sprocket 34 which is rotated clockwise or counterclockwise, depending upon the necessity to cause the scaffold or any other weight attached to cable 24 to ascend or descend. Sprocket 34 is attached to a clutch unit 35 which is driven by the shaft 33 of motor 17. Clutch 35 performs two different functions: (a) it serves as a means to disengage the motor 17 from the other elements of the driving mechanism if the winch is desired to be operated manually by handle 56; and (b) it is designed in a manner to disengage the motor from the other elements of the driving mechanism in the event that a too heavy load is placed on the scaffold or that the scaffold has been caught by some obstruction on the face of the structure. The rotation of cable drum 25 immediately ceases upon the disengagement of clutch unit 35.

Sprocket 34 drives a roller chain 36 which in turn drives sprocket 37 on shaft 38, sprocket 37 being keyed to the latter. Shaft 38 operates a spring clutch unit 39 which in turn transmits the rotation to gear 41 mounted on shaft 43 by the pinion 40. The manner of operation of this spring clutch unit 39 will be described in more detail hereinafter, in connection with Fig. 8.

. As stated, pinion 4t) drives gear 41 which is rotatably mounted on the hub extension 44 of a gear 42 mounted on shaft 43 (see Fig. 4). The bore of gear 41 is internally threaded to match the external threads cut on the hub extension 44 of gear 42. Shaft 43 also carries a plain plate ratchet 45 (Figs. 2 and 4) between gears 41 and 42. The bore of ratchet 45 is larger than the outside diameter of threads on the hub 44 of gear 42 and therefore ratchet 45 rotates freely thereon. Pawl 46, mounted on shaft 38, permits the rotation of ratchet 45 in counterclockwise direction only. When gear 41 is rotated in counterclockwise direction by pinion 40, it rotates upon the threaded hub 44 of gear 42 and is thereby forced to move toward gear 42 until stopped by plain plate ratchet 45. As gear 41 is forced to rotate, it tends to clamp ratchet 45 between itself and gear 42 and therefore gear 41, ratchet 45 and gear 42 all rotate in unison and pawl 46 merely rides over the teeth of the ratchet 45, when the ratchet 45 rotates. If gear 41 is rotated in the opposite direction, it backs away from plate ratchet 45 until it hits a stop 47 on the hub extension 44 of gear 42 and thus no longer rotates freely on the threads of hub 44; it forces gear 42 to rotate in unison with it on shaft 43.

The backing away of gear 41 from gear 42 automatically unclamps ratchet 45 which is held stationary by pawl 46. When gear 41 hits the stop 47, it rotates in unison with pinion 42 and the cable may unreel from drum 25. If the rotation of gear 41 is stopped, then the tension in cable 24, working through cable drum 25, shaft 26, ratchet 48, pawls 49, 49a (see Fig. 2) and bolts 50, 50a, in that order, causes gear 51 to rotate counterclockwise and thereby causes gear 42 to rotate in clockwise direction. 'This rotation causes gear 41 to move toward gear 42 and to clamp ratchet 45 between them, as previously described. However, since the direction of the teeth of ratchet 45 is opposed to the pawl 46, all motion of pinion gear 42 stops. This action is automatic and therefore the described arrangement constitutes an automatic braking device to restrain the winch from lowering the scaffold or the like, attached to cable 24, under the force of gravity of said scaffold, except when driven by gear 40.

In normal operation, pinion 42 meshes with a gear 51 mounted on shaft 26. Pinion 42 rotates said gear 51 in clockwise direction when the cable 24 is spooled onto cable drum 25, and in counterclockwise direction when cable 24 is being unreeled from the drum. Gear 51 rotates freely on shaft 26. As this gear 51 rotates, it forces pawls 49, 4% against the teeth of ratchet 48 which is keyed onto shaft 26 (see Fig. 2). Pawls 49, 45a are fastened to gear 51 by means of shouldered cap screws 50, 50a and are free to rotate upon the shoulders of the screws. Leaf springs 53, 53a are attached to pawls 49, 49a and bear against the projecting rim of gear 51, thereby keeping pawls 49, 49a normally in engagement with the teeth of ratchet 48. Ratchet 43 is keyed non-rotatably to shaft 26 and thus in turn rotates cable drum 25 to reel or unreel cable 24.

The tension in the cable 24 tends to rotate ratchet 48 through cable drum 25 and shaft 26 in counterclockwise direction and thereby keeps the teeth of ratchet 48 in contact with pawls 49, 49a.

If the motor 17 drives gears 41), 41, 42, 51 in the lowering direction, pawls 49, 49a tend to disengage from the teeth of ratchet 48. However, the tension in cable 24 resulting from the weight of the scaffold attached thereto tends to rotate the ratchet 48 in the same direction and keeps paw1s49, 49a in engagement with the teeth of ratchet 48.

The main reason for driving shaft 26 from gear 51 through ratchet 48 and pawls 49, 49a is that this manner of driving provides a simple and reliable means of disengaging cable drum 25 from the rest of the driving mechanism by merely prying pawls 49, 490 out of engagement and clear of the teeth of ratchet 48 and inserting a pair of pins into holes 54, 54a and letting part of these pins to project into similar aligned holes in gear 51. The pins hold pawls 49, 49:: clear of the teeth of ratchet 48 and thus ratchet 48, shaft 26 and cable drum 25 are free to rotate independently of the driving mechanism. The cable 24 can be readily unreeled from drum 25 when, for example, rigging the winch for operation. Other advantage of this ratchet and pawl combination is in that it prevents cable 24 from being wound on the drum 25 in the wrong direction, and should cable 24 jam while it is being unreeled, the drive will merely ratchet. This combination also permits the use of a locking or safety pawl 55, as shown in Fig. 6, without any danger of overloading the driving mechanism. This pawl 55 ratchets on ratchet of disc 32a shown in Fig. 3.

The main feature of my novel winch is the use of the friction brake in combination with a one-way brake, consisting of a spring clutch and a ratchet, in the same scaffolding machine, either of which can hold the load by itself. However, by the novel way of combining both brakes in a single winch, each brake is capable of olfsetting the weak points of the other brake by its own strong points.

The spring clutch 39, shown in more detail in Fig. 8, is mounted on shaft 38. This clutch, which works independently of the rest of the system, does not depend on the friction of the driving mechanism as the abovedescribed friction brake. It is housed in an elongated cylindrical shell 60 and a cylindrical sleeve 61 abutting said shell 60 and having a reinforcing ring 62 which partly fits over shell 60 to prevent entry of foreign material into the spring clutch. Shell 60 carries a ratchet wheel 63 assess-4.

cooperating with pawl 64 mounted on bolt 65, as seen inFig. l and in more detail in Fig. 5. Bearings 84 and 84a reduce the friction of shaft 38 within shells 12, 13.

Sleeve 61 is either integral or firmly connected to pinion 40, the pinion having a bore 38a for the passage of shaft 38. Sleeve 61 has a segmental cutout 66 limited by walls 67 and 68. Within sleeve 61 and shell 60 is a cylindrical member 69 which is keyed to shaft 38, the slot to receive key 74 being shown at 70. One end of the cylindrical member 69 which is adjacent the closing wall 71 of shell 65) has a collar 72 which is interrupted at 73 to form a slot therein into which one end ofspring 76 fits, as will be explained in more detail hereinafter. The other end of cylindrical member 69 which is within sleeve 61 is provided with a projection 75 to loosely fit into the segmental cutout 66. This segmental cutout 66 prevents independent rotation of member 69 with respect to sleeve 61 in case that the spring 76 should break or become displaced, or excessively worn.

. The spring 76-consists of a cylindrically wound band 77 with both ends 78 and 78a bent in a direction parallel to the axis of the spring. End 78 fits into the slot 73 of collar 72 in cylindrical member 69, and end 78a fits into a hole 73b bored into the wall 61a of sleeve 61; When inserted into the spring clutch 39, the spring 76 surrounds with its convolutions 77 the cylindrical member 69 within shell 60 and sleeve 61. The diameter 6f spring 76 is slightly larger than the diameter of the bores of shell 60 and sleeve 61; therefore, its convolutions must be slightly compressed when inserted into shell 60 and sleeve 61 of the spring clutch.

The operation of the clutch 39 is as follows:

When shaft 38 is rotated in a clockwise direction, either by chain 36 from c'lutch 35, or by handle 56, it rotates the cylindrical member 69 which is keyed to shaft" 38 by key 74 insertable into slot 70 of member 69 and slot 73a of shaft 33. The wall of the slot 73 in collar 72 of member 69 bears against end 78 of spring 76. This causes the convolutions 77 to expand radially and to press more tightly against the inner surfaces of shell 60 and sleeve 61, thus rotating both shell 60 and sleeve 61 in clockwise direction, pawl 64 riding loosely over the teeth of ratchet 63. The end 78a of spring 76 is forced against the wall of bore 73b and thus additionally causes sleeve 61 with pinion 46 to rotate in the clockwise direction. The rotation of pinion 40 causes gear 41 and pinion 42 on shaft 43 to rotate counterclockwise'and the gear 51 on shaft 26 to rotate clockwise and to reel the cable 24 onto cable drum 25.

When motor 17 is stopped, or the rotation of shaft 38 by crank 56 ceases, the tension in cable 24 tends to rotate gear 51 in counterclockwise direction, this in turn tending to rotate pinion 42 and gear 41 in clockwise and pinion 46' with sleeve 61 in counterclockwise direction. The wall of hole 731) is then forced against the end 78a of spring 76 and tends to expand the spring 76 which in turn causes the spring to more firmly adhere to the inner surfaces of shell 60 and sleeve 61 and tends to rotate the same in counterclockwise direction. However, ratchet 63 which is secured to or integral with shell 60, is prevented from rotation in the counterclockwise direction by pawl 64 and thus any rotation in counterclockwise direction of shaft 38 is prevented.

If it is desired to unreel cable 24 from drum 25, shaft 38 is rotated in counterclockwise direction. Then, cylindrical member 69 which is keyed to shaft 38, also rotates in counterclockwise direction and causes wall of slot 73 in cylindrical member 69 to press against end 78 of spring 76 in counterclockwise direction thus tending to radially compress its convolutions and disengaging spring 76 from the inside surface of shell 60 and allowing the outer surface of spring 76 to slide within the bore of shell 60 which is held stationary by pawl 64 in engagement with ratchet 63. As the spring 76 slides, the tension of cable 24 then causes the pinion 40 and sleeve 61 to follow the rotation in counterclockwise direction through gear 51, pinion 42 and gear 41.

It may be seen fromthe above that the cable 24 can be unreeled from drum 25 only when the shaft 38 is actually rotated in counterclockwise direction. When the handle is simply released or the motor stopped, the spring 76 will expand radially against the inner surface of shell 60 and enough friction will develop between these two members to cause rotation of spring 76 with respect to shell 60 to cease. Shell 60 is prevented from rotation in the lowering direction by ratchet 63 and pawl 64. The spring clutch will prevent any unreeling of the cable until the shaft 38 is actually rotated anticlockwise by the motor 17 or crank 56. Projection 75 of cyhndrical member 69 has freedom of movement in the segmental cutout 66 within sleeve 61 and does not touch the walls. of sleeve 61 at any time unless the spring 76 should break or wear out. In other words, the angle of the segmental cutout is so proportioned that the spring 76, when in operative condition, bears the load through ends 78and 78a, and does not letprojectidn 75 touch the walls of cutout 66 in sleeve 61 'at any point.

Should the spring 76 break or become displaced, then this'proje'ction 75 comes into contact with either wall 67 or Wall 68 of cutout 66 and transmits the load directly from pinion 40 to cylindrical member 69 and thus to shaft 38, instead through spring 76 which has been displaced or had broken down. This is an additional safety measure in the spring clutch arrangement.

Figs. 6 and 7 show that embodiment of the novel winch wherein the device is operated only manually by crank 56. This structure is essentially the same as the previously described power-driven winch, except that the arrangement of the brakes has been changed and the sheave wheel 21withi-n member slides along the outer surface of bracing bolt 20a without guide pin 27 and grooves 23a; thus, the tension of cable 24 causes its convolutions to arrange themselves around the barrel of cable drum 25 on shaft .26. These two figures also show a ratchet 86 formed on the flange 32a of cable drum barrel 25a, which cooperates with pawl 55 held against the teeth of ratchet 80 by spring 81. This is an additional safety measure and any unwinding of cable 24 from drum 25 is impossible unless pawl 55 is disengaged from the teeth of ratchet 80; when the cable 24 is reeled onto drum 25, the pawl 55 merely rides over the teeth of ratchet 80.

It is evident from the above description of the friction brake and the spring clutch that either of these alone can prevent the unreeling of cable 24 when such unr'eeling is not desired or is dangerous. As mentioned above, it is preferable to place the friction brake closer to the load and the spring clutch closer to the driving mechanism. However, their relative arrangement is such that the load is directly transmitted from the one to the other, which considerably increases the safety of the winch structure since, should the friction brake break or otherwise fail to operate, the spring clutch with ratchet 63 will immediately take up the load and prevent any undesired unreeling of the cable, or vice versa. This relative interconnection is shown in the figures of the drawing by the arrangement of pinion 40 and gear 41. Gear 41 on shaft 43, which together with pinion 42 and its integral hub extension 44, ratchet 45, pawl 46 and stop 47 forms the friction brake, directly transmits the load from gear 51 and thus from cable 24 to pinion 40 and therethrough to the spring clutch. On the other hand, this pinion 40 of spring clutch 39 directly transmits the rotational movement of shaft 38 from either crank 56 or from motor 17 to gear 41 and thus to the friction brake, and through gear 51 to cable drum 25.

Various changes and modifications will occur to persons skilled in the art within the spirit of my invention, and I therefore do not desire to be limited to the exact de- 1 tails of the'above disclosure, the scope of the invention being defined by the appended claims.

I claim:

1. In a scafiolding machine having a support, a casing connected with said support, a first shaft in said casing and a winding drum on said first shaft for reception of a length of cable, one end of said cable being anchored in said drum, the combination of driving means for imparting rotational movement to said drum in clockwise and counterclockwise direction, means rotatable with said drum for distributing said cable on the periphery of said drum when said drum is rotated in a direction to wind said cable thereon, means for disengaging said drum from said driving means, a second shaft in said casing, a friction brake on said second shaft between said driving means and said drum for preventing rotation of said drum while said driving means is not actuated, a third shaft in said casing, a second brake on said third shaft, said second brake including a spring clutch, a ratchet and a pawl, operatively connected between said friction brake and said driving means for preventing rotation of said drum while said driving means is not actuated, and a clutch member between said second brake and said driving means for disengaging said driving means at a predetermined tension in said cable.

2. The structure of claim 1, wherein said drum is non-rotatably attached to said first shaft and said means for disengaging said drum from said drive means includes a gear operatively connected with said drive means and rotatable on said first shaft, a ratchet non-rotatably mounted on said first shaft, a plurality of pawls rotatably supported by said gear, resilient members for urging said pawls into engagement with said ratchet, and means for fixing said pawls upon disengagement thereof from said ratchet.

3. In a scaffolding machine having a support, a casing connected with said support, a first shaft in said casing and a winding drum on said first shaft for reception of a length of cable, one end of said cable being anchored in said drum, the combination of driving means for imparting rotational movement to said drum in clockwise and counterclockwise direction comprising a driving gear on said first shaft, means rotatable with said drum for distributing said length of cable on said drum when said drum is rotated in a direction to wind said cable thereon, means for disengaging said drum from said driving means, a friction brake, a second brake, said friction brake being connected between said driving gear and said second brake, said friction brake having a second shaft rotatably supported in said casing, a pinion on said second shaft meshing with said driving gear on said first shaft and having a threaded hub, an interiorly threaded gear member on said hub, a ratchet on said hub, a pawl engaging said ratchet for limiting its rotation to one direction only, said interiorly threaded gear member being operatively connected with said second brake, and a member fixedly connected to said second shaft for limiting the rotational movement of said interiorly threaded gear member on said threaded hub of said pinion, the rotation of said interiorly threaded gear member in one direction by said driving means via said second brake in one direction toward said ratchet causing frictional engagement of said ratchet with said pinion for rotating the same in a direction common to said interiorly threaded gear member, and the rotation of said interiorly threaded gear member in the opposite direction releasing said ratchet, said second brake having a third shaft, a housing on said third shaft, said housing consisting of two cylindrical elements having a closed end and abutting each other with their open ends, the first of said elements having a pinion member integral therewith, said pinion member receiving rotational movement from said driving means and transmitting said movement to said interiorly threaded gear member of said friction brake on said second shaft, the second of said elements of said housing having a ratchet secured thereto, a pawl for engaging said ratchet to permit its rotation in a direction to wind said cable onto said drum, a cylindrical member in said housing, said cylindrical member being non-rotatably secured to said third shaft, a slot in one extremity of said cylindrical member surrounded by said second element, a recess in said first element, a spring surrounding said cylindrical member and mounted in said housing, one end of said spring being held in said slot and the other end of said spring being held in said recess, the rotation of said pinion member in one direction expanding the convolutions of said spring in said housing to engage said first and said second element and rotate the same in the common direction, and rotation of said pinion member in the opposite direction contracting the convolutions of said spring to permit independent rotation of said first element, and a safety device in said second brake, said safety device comprising a projection on said cylindrical member and a segmental cutout in said first element, said projection being adapted to bear against the walls of said cutout when said spring is rendered inoperative, and a clutch member operatively connected with said driving means for disconnecting said driving means from said pinion member of said second brake on a predetermined tension in said cable.

No references cited. 

